How to upgrade from 10.0 to 10.8.1 and replace ADF .dll depnendency

[VinayKushvaha]

We have an ArcGis .Net based application which is on the version 10.1 and I see the there are many componnet which are using the old ADF .DLL  as well as webControls and javascript like below - 

We want to upgrade the ArcGis enterprise version to 10.8.1 , So for that we have installed the latest ArcGis Enterprise SDK but I do not see any alternative to replace this old  ADF DLL and web controls.  Can we still use this web controls and ADF dll library in 10.8.1  or   we need to rewrite all, This is the confusion. 

We will prefer the path which can take minimum changes and impect.  But dont't know how,  Could anyone suggest the the best step by step way, How to achieve it.  please. 

Thanks in advance !!